Between 1576 and 1624, there were at least twenty declarations of Latin editions of the De sphaera and one of Francesco Pifferi’s Italian-language version in the Frankfurt Book Fair Catalogues. These declarations are not straightforward. Some are editions, and some are reissues; some are associated with the names not of the publisher but of the bookstore through where they were on offer. In some cases, the year of declaration and the place of publication are misleading, and, in the case of the Christophorus Clavius commentaries, the claim made about the number of the edition (whether third, fourth, fifth, or “seventh”) is false. The aim of this paper is to elucidate how the fairs operated, to identify which edition is in question, to place these in the context of the Catholic, Lutheran, and Reformed pedagogy of the period, and to show how producers, advertisers, and commissioning agents of the Sacrobosco Sphaera editions interacted, with special reference to the editions of Rome and Venice (and their publishers the Basa family and Giovanni Battista Ciotti), and those of Lyon and St. Gervais (and their publishers de Gabiano and Samuel Crespin). The final case considered is the declaration in 1624 of the edition of the Jesuit Bernardus Morisanus produced by the Reformed printer-publisher Peter Mareschal, as an element in a cursus philosophicus.